Cavity PCB plays an important role in reducing the size of electronic products. Compared with standard PCB, cavity PCB has structural grooves for other functions. The main driving forces of the cavity are thermal management and miniaturization of electronic equipment. There are many ways to make Cavity PCB. What’s the difference between fingertips?
The Cavity PCB provides space for electronic components such as capacitors, transistors and logic modules, making the assembled PCB generally thinner. They can be applied to multilayer PCBs, and if used on a single circuit board, they can provide different layouts of multiple cavities with different depths.
PCB manufacturers provide a variety of ways to create PCB cavities. Most of the cavity plates are manufactured by controllable deep milling process and equipped with special milling machine. If necessary, the cavity can be electroplated. Another way to produce cavities is to laminate them sequentially by a low or no flow prepress. The third method is through the laser depth control.
It is a feasible technology to use cavity in PCB as a method to reduce the component height or increase the component gap. The SMT test of cavity boards assembled with 0.4mm BGA packages at multiple cavity depths shows that PCB can be successfully printed, assembled and reflow in the same multistage process using the existing device functions.
One pass, multi-stage solder paste printing is the most challenging aspect of applying cavity technology to mass production environment. The key to successful paste printing is to optimize the key printing parameters.
- Air gap between pad and cavity wall;
- Length and thickness of scraper;
- Support of printing fixture;
- Alignment of pocket template.
Optimizing the printing parameters helps to ensure the quality of multi-stage paste printing, but the parameters may need to be changed as the cavity design changes. The results show that the relationship between the depth of the cavity, the air gap, the length of the flap and the thickness of the flap will affect the printing result of the paste. Test print is required to reset key parameters to accommodate design differences. Other printing parameters not mentioned in this paper are also important for achieving consistent solder paste quantity through single-stage solder paste printing, and these parameters are also important for multi-stage printing.